My approach is slightly different to Rico's in that I have two HDDs in my PC, one for 'data' (the junk I collect - A bit like Rico's multitude of CD spools) and the other for 'system' files (ie windows). The advantage of this is that I can reformat the system drive any time I like without affecting the data I have on the PC. You can do this with a single drive too by partitioning it into 2 'logical' drives, and using c: for your system, and d: for your data. Obviously, whichever route you choose, you should always ensure that you have your data backed-up on a remote device (like an external hard drive) in case something major should befall your PC. For example, my airshow photos (of which there are many) are on my second drive in the PC where I can get at them quickly, on an external hard drive at home (which is not kept with the PC) and on another which I keep at my parents place, and is updated periodically.
~S~ Jabo